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ASN Wikibase Occurrence # 133815
Last updated: 26 August 2021
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Date:14-MAY-1998
Time:18:10
Type:Silhouette image of generic B06 model; specific model in this crash may look slightly different
Bell 206B
Owner/operator:Pacific Rotor
Registration: N90215
MSN: 1698
Fatalities:Fatalities: 0 / Occupants: 1
Other fatalities:0
Aircraft damage: Written off (damaged beyond repair)
Category:Accident
Location:Temecula, CA -   United States of America
Phase: Take off
Nature:Agricultural
Departure airport:
Destination airport:
Investigating agency: NTSB
Narrative:
HISTORY OF FLIGHT

On May 14, 1998, at 1810 hours Pacific daylight time, a Bell 206B, N90215, experienced a loss of power in the takeoff initial climb and crashed in a field approximately 2 miles west of the Temecula, California, airport. The aircraft was destroyed; however, the commercial pilot, the sole occupant, was not injured. The aerial application flight, conducted under 14 CFR Part 137, originated from Fallbrook, California, at 0645 and had made multiple refueling stops in the fields being worked. Visual meteorological conditions prevailed and no flight plan was filed.

The pilot reported that he had been spraying local avocado groves. He had loaded the aircraft with 90 gallons of spray materials and was taking off. Just after the helicopter passed through translational lift, the aircraft yawed and the pilot noticed a decrease in engine noise. The pilot reported that at that time, he was about 10 feet agl over sloping terrain. The aircraft settled and impacted the ground. The pilot stated that the engine was still spooling down as he exited through the right side door.

ENGINE EXAMINATION

The Safety Board conducted a teardown inspection of the airframe and powerplant on June 22, 1998. Basic control continuity was established. Visual examination of the compressor inlet showed blade and vane distress commencing at the third stage. A full report of the inspection is appended to this file.

TESTS AND RESEARCH

The compressor case halves, compressor rotor assembly, and compressor front support were sent to the Safety Board Materials Laboratory for further examination. A copy of the metallurgist's report is appended to this file.

The compressor case is composed of two longitudinal halves with an attached inlet guide vane (IGV) assembly. The IGV's are part of the compressor front support that is mounted to the forward flange of the compressor case halves. When assembled and operational, air first enters the compressor through the inlet guide vane assembly, then passes through six stages of axial compression and a final centrifugal compressor stage. Each stage of axial compression is composed of a rotating set of compressor blades followed by a fixed set of stator vanes.

None of the compressor blades were fractured; however, the blades did exhibit impact damage on the trailing edges of the third stage through the centrifugal compressor stage. The fourth and fifth stages displayed chipping, bending, and curling of the individual blades, with the bending in the direction opposite of rotation. Some leading edge tip erosion was also noted on the first stage blades.

Each compressor case half has six rows (stages) of radially oriented vanes projecting inward from the case shell. In each stage, the vanes are individually attached to separate vane bands that are in turn attached to the case halves. The inside diameter of the case assembly is covered by a thick plastic erosion coating. Many of the vanes in the third and fourth stages were fractured, particularly in the lower case half. The remaining vanes in these stages exhibited scarring and bending. The vane bending was in the direction of rotation. Several of the remaining third stage vanes were bent slightly forward and into the rotational path of the third stage rotor and exhibited machining. Vanes in stages four and five also displayed damage, but none of the vanes had separated.

In the third stage, 11 of the 28 total vanes were fractured, and 23 of the 32 vanes in the fourth stage were also fractured. Subsequent visual and magnified examinations found that all of the vane fracture surfaces had been smeared by post-separation mechanical damage.

A spiraling path of erosion was visible in the plastic case liner material. The erosion path was visible through the first four vane stages and was most evident in the lower case half. Beginning with the first stage vanes, the erosion had completely abraded through the plastic to the vane band adjacent to five vanes. At the second

Sources:

NTSB id 20001211X10127


Revision history:

Date/timeContributorUpdates
21-Dec-2016 19:26 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]

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